Chapter 20: The Cardiovascular System

Chapter 20 The Cardiovascular System: The Heart Brachiocephalic trunk Superior vena cava Right pulmonary artery Right pulmonary veins RIGHT AURICLE OF RIGHT ATRIUM Right coronary artery RIGHT ATRIUM CORONARY SULCUS Anterior cardiac vein RIGHTVENTRICLE Inferior vena cava Left common carotid artery Left subclavian artery Arch of aorta Ascending aorta Ligamentum arteriosum Left pulmonary artery Pulmonary trunk Left pulmonary veins LEFT AURICLE OF LEFT ATRIUM Left coronary artery (anterior interventricular branch) ANTERIOR INTERVENTRICULAR SULCUS Greater cardiac vein LEFT VENTRICLE Descending aorta Heart pumps over 1 million gallons per year Over 60,000 miles of blood vessels 1 Heart Location Heart Right lung Aorta Sternum Muscle Left lung Esophagus Sixth thoracic vertebra Heart is located in the mediastinum area from the sternum to the vertebral column and between the lungs 2 Heart Orientation Apex - directed anteriorly, inferiorly and to the left Base - directed posteriorly, superiorly and to the right Anterior surface - deep to the sternum and ribs Inferior surface - rests on the diaphragm Right border - faces right lung Left border (pulmonary border) - faces left lung 3 Heart Orientation Superior vena cava BASE OF HEART Right lung RIGHT BORDER Rib (cut) INFERIOR SURFACE Diaphragm Arch of aorta Pulmonary trunk Left lung LEFT BORDER APEX OF HEART Heart has 2 surfaces: anterior and inferior, and 2 borders: right and left 4 Surface Projection of the Heart Superior left point Superior right point Inferior right point Inferior left point Superior right point at the superior border of the 3rа right costalcartilage Superior left point at the inferior border of the 2nd left costal cartilage 3cm to the left of midline Inferior left point at the 5th intercostal spaаce, 9 cm from the midline Inferior right point at superior border of the 6th right costal cařtilage, 3 cm from the midline 5 Pericardium FIBROUS PERICARDIUM PARIETAL LAYER OF SEROUS PERICARDIUM Pericardial cavity VISCERAL LAYER OF SEROUS PERICARDIUM (EPICARDIUM) PERICARDIUM Heart wall ENDOCARDIUM Trabeculae carneae Coronary blood vessels MYOCARDIUM (CARDIAC MUSCLE) Fibrous pericardium dense irregular CT protects and anchors the heart, prevents overstretching Serous pericardium thin delicate membrane contains parietal layer-outer layer pericardial cavity with pericardial fluid Layers of Heart Wall FIBROUS PERICARDIUM PARIETAL LAYER OF SEROUS PERICARDIUM Pericardial cavity VISCERAL LAYER OF SEROUS PERICARDIUM (EPICARDIUM) PERICARDIUM Heart wall ENDOCARDIUM Trabeculae carneae Coronary blood vessels MYOCARDIUM (CARDIAC MUSCLE) Epicardium visceral layer of serous pericardium Myocardium cardiac muscle layer is the bulk of the heart Endocardium chamber lining & valves 7 Muscle Bundles of the Myocardium Superior vena cava Aorta Pulmonary trunk Superficial muscle bundles in atria Deep muscle bundle in ventricle Superficial muscle bundles in ventricles Cardiac muscle fibers swirl diagonally around the heart in interlacing bundles 8 Chambers and Sulci of the Heart Four chambers 2 upper atria 2 lower ventricles Sulci - grooves on surface of heart containing coronary blood vessels and fat coronary sulcus ■encircles heart and marks the boundary between the atria and the ventricles anterior interventricular sulcus marks the boundary between the ventricles anteriorly posterior interventricular sulcus marks the boundary between the ventricles posteriorly 9 Chambers and Sulci Brachiocephalic trunk Superior vena cava Right pulmonary artery Right pulmonary veins RIGHT AURICLE OF RIGHT ATRIUM Right coronary artery RIGHT ATRIUM CORONARY SULCUS Anterior cardiac vein RIGHT VENTRICLE Inferior vena cava H.R Min Left common carotid artery Left subclavian artery Arch of aorta Ascending aorta Ligamentum arteriosum Left pulmonary artery Pulmonary trunk Left pulmonary veins LEFT AURICLE OF LEFT ATRIUM Left coronary artery (anterior interventricular branch) ANTERIOR INTERVENTRICULAR SULCUS Greater cardiac vein LEFT VENTRICLE Descending aorta Anterior View 10 Chambers and Sulci Left common carotid artery Left subclavian artery Arch of aorta Descending aorta Left pulmonary artery Pulmonary trunk Left pulmonary veins LEFT AURICLE OF LEFT ATRIUM LEFT ATRIUM Coronary sinus LEFT VENTRICLE Middle cardiac vein POSTERIOR INTERVENTRICULAR SULCUS R.Muihos Posterior View Brachiocephalic trunk Superior vena cava Ligamentum arteriosum Ascending aorta Right pulmonary artery Right pulmonary veins RIGHT ATRIUM Right coronary artery RIGHT VENTRICLE Inferior vena cava 11 Right Atrium Opening of superior vena cava Fossa ovalis in interatrial septum RIGHT ATRIUM Opening of coronary sinus Opening of inferior vena cava TRICUSPID VALVE Inferior vena cava Receives blood from 3 sources superior vena cava, inferior vena cava and coronary sinus Interatrial septum partitions the atria Fossa ovalis is a remnant of the fetal foramen ovale Tricuspid valve Blood flows through into right ventricle has three cusps composed of dense CT covered by 12 Right Ventricle PULMONARYSEMILUNAR VALVE TRICUSPID VALVE RIGHT VENTRICLE TRABECULAE CARNEAE CHORDAE TENDINEAE INTERVENTRICULAR SEPTUM PAPILLARY MUSCLE LEFT VENTRICLE Forms most of anterior surface of heart Papillary muscles are cone shaped trabeculae carneae (raised bundles of cardiac muscle) Chordae tendineae: cords between valve cusps and papillary muscles Interventricular septum: partitions ventricles Pulmonary semilunar valve: blood flows into pulmonary trunk Left Atrium Left pulmonary veins LEFT ATRIUM AORTIC SEMILUNAR VALVE BICUSPID VALVE CHORDAE Forms most of the base of the heart Receives blood from lungs - 4 pulmonary veins (2 right + 2 left) Bicuspid valve: blood passes through into left ventricle has two cusps to remember names of this valve, try the pneumonic LAMB ■ Left Atrioventricular, Mitral, or Bicuspid valve Left Ventricle TRABECULAE CARNEAE AORTIC SEMILUNAR VALVE BICUSPID VALVE CHORDAE TENDINEAE INTERVENTRICULAR SEPTUM PAPILLARY MUSCLE LEFT VENTRICLE Forms the apex of heart Chordae tendineae anchor bicuspid valve to papillary muscles (also has trabeculae carneae like right ventricle) Aortic semilunar valve: blood passes through valve into the ascending aorta just above valve are the openinas to the coronary15 Myocardial Thickness and Function ■ Thickness of myocardium varies according to the function of the chamber Atria are thin walled, deliver blood to adjacent Ventricleswalls are much thicker and stronger right ventricle supplies blood to the lungs (little flow resistance) left ventricle wall is the thickest to supply systemic16 Thickness of Cardiaс Walls POSTERIOR Transverse plane View Right ventricle Interventricular septum ANTERIOR Left ventricle Myocardium of left ventricle is much thicker than the right. 17 Fibrous Skeleton of Heart Pulmonary semilunar valve Aortic semilunar valve Left coronary artery Bicuspid valve Fibrous skeleton Right coronary artery Tricuspid valve Dense CT rings surround the valves of the heart, fuse and merge with the interventricular septum Support structure for heart valves Insertion point for cardiac muscle bundles Electrical insulator between atria and ventricles prevents direct propagation of AP's to ventricles 18 Atrioventricular Valves Open BICUSPID VALVE CUSPS Open CHORDAE TENDINEAE Slack PAPILLARY MUSCLE Relaxed A-V valves open and allow blood to flow from atria into ventricles when ventricular pressure is lower than atrial pressure occurs when ventricles are relaxed, chordae tendineae are slack and papillary muscles are relaxed 19 Atrioventricular Valves Close BICUSPID VALVE CUSPS Closed CHORDAE TENDINEAE Taut PAPILLARY MUSCLE Contracted A-V valves close preventing backflow of blood into atria occurs when ventricles contract, pushing valve cusps closed, chordae tendinae are pulled taut and papillary muscles contract to pull cords and prevent cusps from everting 20 Semilunar Valves Pulmonary semilunar valve Aortic semilunar valve Left coronary artery Bicuspid valve Fibrous skeleton Right coronary artery Tricuspid valve SL valves open with ventricular contraction allow blood to flow into pulmonary trunk and aorta SL valves close with ventricular relaxation prevents blood from returning to ventricles, blood fills valve cusps, tightly closing the SL valves 21 Valve Function Review Pulmonary semilunar valve (closed) Left coronary artery Bicuspid valve (open) Aortic semilunar Aortic semilunar valve (closed) valve (open) Right coronary artery Bicuspid valve (closed) Tricuspid valve (open) Pulmonary semilunar valve (open) Which side is anterior surface? What are the ventricles doing? Tricuspid valve (closed) 22 Valve Function Review Pulmonary semilunar valve (closed) Left coronary artery Bicuspid valve (open) Aortic semilunar Aortic semilunar valve (closed) valve (open) Right coronary artery Bicuspid valve (closed) Tricuspid valve (open) Pulmonary semilunar valve (open) Atria contract, blood fills ventricles through A-V valves Tricuspid valve (closed) Ventricles contract, blood pumped into aorta and pulmonary trunk through SL valves 23 Blood Circulation Two closed circuits, the systemic and pulmonic Systemic circulation left side of heart pumps blood through body left ventricle pumps oxygenated blood into aorta aorta branches into many arteries that travel to organs arteries branch into many arterioles in tissue arterioles branch into thin-walled capillaries for exchange of gases and nutrients deoxygenated blood begins its return in venules4 Blood Circulation (cont.) Pulmonary circulation right side of heart pumps deoxygenated blood to lungs right ventricle pumps blood to pulmonary trunk pulmonary trunk branches into pulmonary arteries pulmonary arteries carry blood to lungs for exchange of gases oxygenated blood returns to heart in pulmonary veins 25 Blood Circulation 4. In pulmonary capillaries, blood loses CO, and gains O 3. Pulmonary trunk and pulmonary arteries 5. Pulmonary veins (oxygenated blood) A Pulmonary semilunar valve 2. 6. Right ventricle Left atrium 1. A Tricuspid valve Right atrium (deoxygenated blood) Bicuspid valve 7. Left ventricle Aortic semilunar valve 10. Superior vena cava Inferior vena Coronary sinus 8. cava Aorta and systemic arteries 9. In systemic capillaries, blood loses O₂ and gains CO2 Blood flow blue = deoxygenated red = oxygenated 26 Coronary Circulation Coronary circulation is blood supply to the heart ■ Heart as a very active muscle needs lots of O2 When the heart relaxes high pressure of blood in aorta pushes blood into coronary vessels Many anastomoses connections between arteries supplying blood to the same region, provide alternate routes if one artery becomes occluded 27 Coronary Arteries Ascending aorta RIGHT CORONARY Right atrium MARGINAL BRANCH Right ventricle Arch of aorta LEFT CORONARY Pulmonary trunk Left auricle CIRCUMFLEX BRANCH ANTERIOR INTERVENTRICULAR BRANCH Left ventricle POSTERIOR INTERVENTRICULAR BRANCH Branches off aorta above aortic semilunar valve Left coronary artery circumflex branch in coronary sulcus, supplies left atrium and left ventricle anterior interventricular art. supplies both ventricles Right coronary artery marginal branch in coronary sulcus, 28 Coronary Veins Superior vena cava Right atrium ANTERIOR CARDIAC Right ventricle SMALL CARDIAC Inferior vena cava Pulmonary trunk Left auricle CORONARY SINUS GREAT CARDIAC Left ventricle NA. Muinot MIDDLE CARDIAC Collects wastes from cardiac muscle Drains into a large sinus on posterior surface of heart called the coronary sinus Coronary sinus empties into right atrium 29 Cardiac Muscle Histology Desmosomes Mitochondrion Intercalated discs Opening of transverse tubule Gap junctions Cardiac muscle fiber Nucleus Sarcolemma (a) Cardiac muscle fibers Branching, intercalated discs with gap junctions, involuntary, striated, single central nucleus per cell 30 Cardiac Myofibril Nucleus Sarcolemma Transverse tubule Mitochondrion Sarcoplasmic reticulum Z dísc M line Z disc T H zone I band A band I band Sarcomere Thin filament Thick filament 31 Conduction System of Heart SINOATRIAL (SA) NODE 2 ATRIOVENTRICULAR (AV) NODE Right atrium Right ventricle Arch of aorta Left atrium 3 ATRIOVENTRICULAR (AV) BUNDLE (BUNDLE OF HIS) 4 RIGHT AND LEFT BUNDLE BRANCHES Left ventricle 5 CONDUCTION MYOFIBERS (PURKINJE FIBERS) Coordinates contraction of heart muscle. 32 Conduction System of Heart Autorhythmic Cells Cells fire spontaneously, act as pacemaker and form conduction system for the heart SA node cluster of cells in wall of Rt. Atria begins heart activity that spreads to both atria excitation spreads to AV node AV node in atrial septum, transmits signal to bundle of His AV bundle of His the connection between atria and ventricles divides inţo bundle branches & purkinje fibers, large diameter fibers that conduct sighals quickly 33 Π Rhythm of Conduction System SA node fires spontaneously 90-100 times per minute AV node fires at 40-50 times per minute If both nodes are suppressed fibers in ventricles by themselves fire only 20-40 times per minute Artificial pacemaker needed if pace is too slow Extra beats forming at other sites are called ectopic pacemakers 34 Timing of Atrial & Ventricular Excitation SA node setting pace since is the fastest In 50 msec excitation spreads through both atria and down to AV node 100 msec delay at AV node due to smaller diameter fibers- allows atria to fully contract filling ventricles before ventricles contract In 50 msec excitation spreads through both ventricles simultaneously 35 Millivolts (mV) Electrocardiogram---ECG or EKG R 1.0 0.5 S-T segment 4 T P 이 Q P-Q interval S -0.5 Q-T interval 0 0.2 0.4 0.6 0.8 EKG P Action potentials of all active cells can be detected and recorded wave atrial depolarization P to Q interval conduction time from atrial to ventricular excitation QRS complex ventricular depolarization T wave ventricular repolarization One Cardiac Cycle At 75 beats/min, one cycle requires 0.8 sec. systole (contraction) and diastole (relaxation) of both atria, plus the systole and diastole of both ventricles End diastolic volume (EDV) volume in ventricle at end of diastole, about 130ml End systolic volume (ESV) volume in ventricle at end of systole, about 60ml Stroke volume (SV) the volume ejected per beat from each ventricle, about 70ml SV = EDV - ESV 37 Phases of Cardiac Cycle Isovolumetric relaxation brief period when volume in ventricles does not change--as ventricles relax, pressure drops and AV valves open Ventricular filling rapid ventricular filling:as blood flows from full atria diastasis: as blood flows from atria in smaller volume atrial systole pushes final 20-25 ml blood into ventricle Ventricular systole ventricular systole isovolumetric contraction ■ brief period, AV valves close before SL valves open 38 ventricular ejection: as SL valves open and blood is Ventricular Pressures Blood pressure in aorta is 120mm Hg Blood pressure in pulmonary trunk is 30mm Hg Differences in ventricle wall thickness allows heart to push the same amount of blood with more force from the left ventricle The volume of blood ejected from each ventricle is 70ml (stroke volume) Why do both stroke volumes need to be same? 39 Auscultation Stethoscope Sounds of heartbeat are from turbulence in blood flow caused by valve closure first heart sound (lubb) is created with the closing of the atrioventricular valves second heart sound (dupp) is created with the closing of semilunar valves 40 Heart Sounds 6 5 4 1 2 3 Pulmonary semilunar valve Aortic semilunar valve Bicuspid valve Tricuspid valve Where to listen on chest wall for heart sounds. 41 Cardiac Output Amount of blood pushed into aorta or pulmonary trunk by ventricle Determined by stroke volume and heart rate CO = SV x HR at 70ml stroke volume & 75 beat/min----5 and 1/4 liters/min entire blood supply passes through circulatory system every minute Cardiac reserve is maximum output/output at rest ic 1-5 wbile athlete ic 7-842 Influences on Stroke Volume Preload (affect of stretching) Frank-Starling Law of Heart more muscle is stretched, greater force of contraction more blood more force of contraction results Contractility autonomic nerves, hormones, Ca+2 or K+ levels Afterload amount of pressure created by the blood in the way 43 Congestive Heart Failure Causes of CHF coronary artery disease, hypertension, MI, valve disorders, congenital defects Left side heart failure less effective pump so more blood remains in ventricle heart is overstretched & even more blood remains blood backs up into lungs as pulmonary edema suffocation & lack of oxygen to the tissues Right side failure fluid builds up in tissues as peripheral edema 44 Risk Factors for Heart Disease Risk factors in heart disease: high blood cholesterol level high blood pressure cigarette smoking obesity & lack of regular exercise. Other factors include: diabetes mellitus genetic predisposition male gender high blood levels of fibrinogen left ventricular hypertrophy 45 Plasma Lipids and Heart Disease Risk factor for developing heart disease is high blood cholesterol level. promotes growth of fatty plaques Most lipids are transported as lipoproteins low-density lipoproteins (LDLs) high-density lipoproteins (HDLS) very low-density lipoproteins (VLDLs) HDLs remove excess cholesterol from circulation LDLs are associated with the formation of fatty plaques VLDLs contribute to increased fatty plaque formation There are two sources of cholesterol in the body: 46 Desirable Levels of Blood Cholesterol for Adults TC (total cholesterol) under 200 mg/dl LDL under 130 mg/dl HDL over 40 mg/dl Normally, triglycerides are in the range of 10- 190 mg/dl. Among the therapies used to reduce blood cholesterol level are exercise, diet, and drugs. 47 Exercise and the Heart Sustained exercise increases oxygen demand in muscles. Benefits of aerobic exercise (any activity that works large body muscles for at least 20 minutes, preferably 3-5 times per week) are; increased cardiac output increased HDL and decreased triglycerides improved lung function decreased blood pressure weight control. 48 Coronary Artery Disease Transverse section Atherosclerotic plaque Partially obstructed lumen (space through which blood flows) Heart muscle receiving insufficient blood supply narrowing of vessels- --atherosclerosis, artery spasm or clot atherosclerosis-- smooth muscle & fatty deposits in walls of arteries Treatment drugs, bypass graft, angioplasty, stent49 Clinical Problems MI = myocardial infarction death of area of heart muscle from lack of O2 replaced with scar tissue results depend on size & location of damage Blood clot use clot dissolving drugs streptokinase or tPA & heparin balloon angioplasty Angina pectoris----heart pain from 50 By-pass Graft Obstruction Ascending aorta Grafted vessel HR Mnos 51 Transluminal Coronary Angioplasty Balloon Atheroscle C plaque Narrowed lumen Coronary of artery artery Balloon catheter with uninflated balloon is threaded to obstructed area in artery When balloon is inflated, it stretches arterial wall and squashes atherosclerotic plaque After lumen is widened, balloon is deflated and catheter is withdrawn 52 Stent in an Artery Lumen of artery Maintains patency of blood vessel Stent 53